The Taurus/STEX mission was to launch the first National Reconnaissance Office (NRO) unclassified payload, the Space Technology Experiment (STEX). The launch vehicle used was Orbital Sciences Corporation'sTaurus rocket in the Air Force configuration (also known as the "ARPA Taurus"). This version of the Taurus rocket uses a Peacekeeper motor as stage 0 rather than the Castor 120 rocket motor that is used in the commercial variation of the Taurus. The Taurus/STEX mission was successfully launched on October 3, 1998 out of Vandenberg AFB.